1. Field of the Invention
This invention relates to an anchorage for anchoring a stressed reinforcing tendon to a structural body, and is particularly concerned with the anchoring of a so-called flat tendon which consists of a plurality of stressed elongate elements arranged to lie side by side generally in a flat array. The invention extends to a structural body having a stressed tendon anchored by at least one anchorage of the invention. By the term "elongate element" herein I mean any element, usually made of steel, which is used for the prestressing of structural bodies or members. Conventionally wire or strand is used, strand being formed by winding a plurality of wires around a single core wire for example seven wire strand or nineteen wire strand. In this specification I shall refer to strand, for convenience, but references to strand can also be taken as reference to the use of wire.
2. Descripiton of the Prior Art
In the construction of post-tensioned concrete slabs, flat tendons are commonly used. FIGS. 1 and of the accompanying drawings show a typical prior art flat tendon anchorage and part of the tendon. For the purpose of illustration, this tendon is shown as composed of four strands 1 of wire, which lie inside a flat sheath 2, whose shape can be seen in FIG. 2 which is a section on the line A--A of FIG. 1. This sheath 2 may also be described as rectangular. Ideally, the strands all lie in a common plane in the sheath 2, but as shown in FIG. 2 there is a tendency for the strands to bunch together in the corners of the sheath, and this arises because the apertures 3 in the anchoring body 4 which receives the strands 1 lie in one line. The strands 1 are individually gripped in the apertures 3 by conventional split conical wedges 5. The strands deviate from one another in a fan shape within the conical trumpet 6 in order to enter the apertures 3.
At the junction of the trumpet 6 and the sheath 2, the strands undergo a lateral (transversal) deflection or bend and therefore tend to bite into each other at this point, which makes it difficult to stress the strands precisely and achieve the desired uniform and accurate tension in the strands.